diff --git a/common/lua/pool.go b/common/lua/pool.go
index 5457ebcf6..ec9a58906 100644
--- a/common/lua/pool.go
+++ b/common/lua/pool.go
@@ -69,6 +69,7 @@ func (p *Pool) Acquire(ctx context.Context) (*glua.LState, error) {
 	n := len(p.idle)
 	if n != 0 {
 		state := p.idle[n-1]
+		p.idle[n-1] = nil
 		p.idle = p.idle[:n-1]
 		p.mu.Unlock()
 		return state, nil